Draft-tube for turbines



H. 0. DAHLx DRAFT TUBE FOR TURBINES.-v

APPLICATION FILED Aue.9, 19u.

Patented Mar'. 2,1920.

' INV SII/Ton:

ATTO RNE( HJALVIAR OLIVIER DAL-IL, F STOCKHOLM, SVJEDEN.

DRAFT-TUBE FOR TURBNES.

.epplication led August 9.

To @ZZ Iwhom it' may concern:

Be it known thatl I, HJALMAR OLIVIER BAHL, a subject of the King of Sweder, and resident of Upplandsgatan No. 60, Stockholm, in the Kingdom of Sweden, have invented certain new and useful Tmprovernents in Draft-Tubes for Turbines, of which the following is a specification, reference being had the-rein to the accompanying drawing.

The present invention refers to an arrangement in draft tubes for reaction and full admission turbines, and is essentially characterized by the fact that there is arranged, immediately at the outlet of the turbine a body or core having a smooth surface and the diameter of which increases in the outlet direction. and that the part of the suction pipe, as it leaves the turbine, is gradually enlarged.; as a result of these arrangements, the water, after having1 passed the runner, will pass annular surfaces of increasing' mean diameter, and con vstant or increasing cross section area in order to effect a higher utilization of the component of rotation of the velocity of the water than is otherwise possible, and to enable a changing of the energy of motionof the water `into energy ,of pressure for a very short distance, whereby the losses in the continuation of the draft tube are reduced. especially when the water-passage is immee y c `ryed, as in suction bends and twin draft tubes.

The invention is further characterized by other arrangements, which will be herein.- after set forth, in connection with some suitable embodiments.

Referring to the accompanying drawings. Figure l illustrates. in section. a forni of the invention in which the core is free of the casing. Fig. 2 illustrates a forni in which the core extends inwardly from the casing, Fig. 3 illustrates a form of'my inyention as embodied in a double turbine apparatus.

in Fig. l, l is the water guide of the turbine, provided with the guide blades lx. 2 is the ruimer of the turbine, fixed to the shaft 2*' which is journaled in suitable bearings, not shown. 8 is Athe draft tube, con neeted with the said water guide.

According to the present invention, a central body or core l is located in the draft tube 3 immediately at the outlet of the turbine. es shown the said gure, the core has a Specification ofletters Patent.

Patented Mar. 2, 1920.

1917. serial no. 155,373.

smooth surface of revolution and the diameter of same increases gradually in the outlet direction. rlhe part of the draft tube 3 surrounding,f the central body 4- and situated nearest to the turbine is gradually enlarged.

The said shape of the top part of the central body and the part of the draft tube surrounding the same forms the essential feature of the invention. The lower part of the body may be shaped as shown, for in-` stance its diameter may gradually decrease or it may be shaped otherwise. The same is the case as to the lower part of the draft tube, which in Fig. l is cylindrical.

Preferably, the central body or core is stationary. in which case. the said body or core #l is fixed to the draft tube 3 by means of ribs six.

The draft tube with the core acts in the following` manner: The water enters the draft tube as indicated by the arrows. As the water leaves the runner, it generally has a. component of rotation. which decreases the distance of the water particle from the axis of the turbine increases. Consequently, the absolute pressure of the water increases while the water passes the top part of the draft tube and the desired changing;` of the energy of motion of the water into energv of pre ure is effected, At the same time. the axial component of velocity of the water is changed into energy of pressure for a. shorter distance than is the case without the central core.

lllhen the water-passage is to be curved, the draft tube and the central body may be shaped as shown in Fig. n that illustration. the central body consists of a bulge formed in the wall of the draft tube 3. This arrangement may evidently, be applied to single turbines as well as to double ones,

with horizontal shaft or vertical shaft and siiit:bly modified, and also in such cases, in which "ienngle between the turbine shaft and the outlet direction of water possibly differs from 90". Owing to the fact that the velocity of the water is rapidly reduced for reasons stated above. the draft tube may be immediately curved"I without great losses of energy,

y in Fia'. 3 is shown a draft tube 3 with two central bodies 4, land adapted for a double turbine with a common outlet for the water. rhe central bodies 4. 4: are connected with one another at their bases as bine, a turbine runner,

shown. This construction ermits the draft tube bend or suction con uit to be materially shortened and broadened.

1. In combination, a draft tube for a turbine and single body within and sur- IOunded by said tube, the' said body having a curved sectional prole and an unobstruotive outer surface, the diameter of said body gradually increasing in the outlet direction, and the inner part of the tubc surrounding said body being gradually enlarged in the said direction.

2. -In combination, a draft tube for a turand a single body Within and surrounded by said tube and loading directly `from the runner, the said body having a curvedsecti'onal proiile and an unobstructing outer surface, the diam-` eter of said body gradually increasing in the outlet direction, and the inner part of the tube, surrounding said body being' gradually enlarged iu the said direction.

3. In combination. a draitii'ibe Jfor a turbine; a rotatable turbine runner; and a singie non-rotatable body Within and surrounded Aby the tube, the surface of the runner leading directly'into that of the body,

said last-named surface'being unobstructing and said body having a curved sectional profile and of a diameter which gradually increases in the outlet direction, and the inpart of the tube surrounding said lbody being gradually enlarged in the same direction.

4. A draft tube for a turbine and a single body projecting into the tube from a Wall thereol and surrounded by part of the tube, the said body having an outer surface, the diameter of which gradually` increases in the outlet direction, and the inner part of the art of the tube surrounding said body being gradually enlarged in the said direction.

5. A draft tube for a'turbine and La single body within the tube and connected with a wall thereof and surrounded by part o'E the tube, tbc said body having an outer surface, the diameter of which gradually increases in. the ,outlet direction, and the inner part of the part of the tubi surrounding said body being gradual y enlarged in the said direction. i

In witness whereof, I have hereunto signed my name.

HJALMAR OLIVIER DAI-IL. 

